Quarterly report pursuant to Section 13 or 15(d)

BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Schedule Of Subsidiaries) (Details)

v3.19.2
BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Schedule Of Subsidiaries) (Details)
6 Months Ended
Jun. 30, 2019
Related Party Transaction [Line Items]  
Entity Address, State or Province OH
Northshore  
Related Party Transaction [Line Items]  
Entity Address, State or Province MN
United Taconite  
Related Party Transaction [Line Items]  
Entity Address, State or Province MN
Tilden  
Related Party Transaction [Line Items]  
Entity Address, State or Province MI
Empire  
Related Party Transaction [Line Items]  
Entity Address, State or Province MI
Metallics  
Related Party Transaction [Line Items]  
Entity Address, State or Province OH